U.S. patent application number 13/118188 was filed with the patent office on 2012-05-03 for integrated 3-dimensional electromagnetic element arrays.
This patent application is currently assigned to California Institute of Technology. Invention is credited to Florian Bohn, Seyed Ali Hajimiri.
Application Number | 20120105182 13/118188 |
Document ID | / |
Family ID | 45996056 |
Filed Date | 2012-05-03 |
United States Patent
Application |
20120105182 |
Kind Code |
A1 |
Bohn; Florian ; et
al. |
May 3, 2012 |
INTEGRATED 3-DIMENSIONAL ELECTROMAGNETIC ELEMENT ARRAYS
Abstract
Systems and methods for constructing integrated three
dimensional electromagnetic element arrays using a bulk resonator
are illustrated. In several embodiments, the integrated three
dimensional electromagnetic element arrays include electromagnetic
elements buried within the bulk resonator. In many embodiments,
inclusion of a third dimension in the electromagnetic element array
can alleviate or eliminate the trade-offs that are experienced in
conventional integrated antennas by using the third physical
dimension to provide an additional degree of freedom to manipulate
electromagnetic boundary conditions in the near-field of the
substrate, affecting both the resulting electromagnetic near- and
far-fields. In several embodiments, three dimensional
electromagnetic element arrays are formed by mechanically stacking
substrates on which integrated planar circuits are formed (i.e.
chips) using conventional die stacking techniques.
Inventors: |
Bohn; Florian; (Campbell,
CA) ; Hajimiri; Seyed Ali; (La Canada, CA) |
Assignee: |
California Institute of
Technology
Pasadena
CA
|
Family ID: |
45996056 |
Appl. No.: |
13/118188 |
Filed: |
May 27, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61349148 |
May 27, 2010 |
|
|
|
Current U.S.
Class: |
335/296 |
Current CPC
Class: |
H01L 2224/48091
20130101; H01Q 1/2283 20130101; H01L 2924/00014 20130101; H01Q
23/00 20130101; H01Q 21/0093 20130101; H01L 2224/48091
20130101 |
Class at
Publication: |
335/296 |
International
Class: |
H01F 7/06 20060101
H01F007/06 |
Claims
1. An integrated 3-dimensional electromagnetic element array,
comprising: a first planar integrated circuit, where the first
planar integrated circuit comprises at least a first integrated
electromagnetic element; and at least a second planar integrated
circuit located on a different plane to the first planar integrated
circuit, where the second planar integrated circuit comprises at
least a second integrated electromagnetic element; wherein the
first and second integrated electromagnetic elements are configured
to control the near- and far-field pattern produced by the
3-dimensional electromagnetic element array.
2. The integrated 3-dimensional electromagnetic element array of
claim 1, wherein: the first planar integrated circuit is formed on
the surface of a bulk resonator; and the second planar integrated
circuit is buried within the bulk resonator.
3. The integrated 3-dimensional electromagnetic element array of
claim 2, further comprising: a plurality of planar integrated
circuits buried at different depths within the bulk resonator,
where each integrated circuit includes at least one integrated
electromagnetic element; wherein the electromagnetic elements are
configured to control the near- and far-field pattern produced by
the 3-dimensional electromagnetic element array.
4. The integrated 3-dimensional electromagnetic element array of
claim 1, wherein the electromagnetic elements are configured to
control the modes excited within the bulk resonator.
5. The integrated 3-dimensional electromagnetic element array of
claim 1, wherein the electromagnetic elements are configured to
control the directionality of energy radiated by the bulk
resonator.
6. The integrated 3-dimensional electromagnetic element array of
claim 1, wherein the electromagnetic elements are configured as an
antenna.
7. The integrated 3-dimensional electromagnetic element array of
claim 1, wherein the antenna is a phased antenna array.
8. The integrated 3-dimensional electromagnetic element array of
claim 1, wherein the electromagnetic elements form part of an
electromagnetic reflector.
9. The integrated 3-dimensional electromagnetic element array of
claim 1, wherein the electromagnetic elements form part of a
shutter.
10. The integrated 3-dimensional electromagnetic element array of
claim 1, wherein the electromagnetic elements form part of a pulsed
source.
11. The integrated 3-dimensional electromagnetic element array of
claim 10, wherein the pulsed source is configured so that the
timing of switching between states is aligned with the delay in the
3-dimensional electromagnetic element array.
12. The integrated 3-dimensional electromagnetic element array of
claim 1, wherein the electromagnetic elements are configured as a
frequency selective filter.
13. The integrated 3-dimensional electromagnetic element array of
claim 1, wherein: the bulk resonator comprises a die stack; the
first planar integrated circuit is located on a first semiconductor
substrate within the die stack; and the second planar integrated
circuit is located on a second semiconductor substrate within the
die stack.
14. The integrated 3-dimensional electromagnetic element array of
claim 13, wherein: the first planar integrated circuit is located
on the surface of the die stack; and the second integrated circuit
is buried within the die stack.
15. The integrated 3-dimensional electromagnetic element array of
claim 13, wherein the die stack further comprises intermediate
dielectric layers.
16. The integrated 3-dimensional electromagnetic element array of
claim 13, wherein at least the first semiconductor region includes
a region having different material properties to the region on
which the first planar integrated circuit is formed.
17. The integrated 3-dimensional antenna of claim 13, further
comprising semiconductor optics formed on the die stack.
18. The integrated 3-dimensional antenna of claim 13, wherein the
electromagnetic elements are configured to control the modes
excited within the die stack.
19. The integrated 3-dimensional antenna of claim 13, wherein the
electromagnetic elements are configured to control the
directionality of the energy radiated by the bulk resonator.
20. The integrated 3-dimensional antenna of claim 13, wherein the
3-dimensional electromagnetic element array is configured as an
antenna.
21. The integrated 3-dimensional antenna of claim 20, wherein the
antenna is a phased antenna array.
22. The integrated 3-dimensional electromagnetic element array of
claim 13, wherein the electromagnetic elements form part of an
electromagnetic reflector.
23. The integrated 3-dimensional electromagnetic element array of
claim 13, wherein the electromagnetic elements form part of a
shutter.
24. The integrated 3-dimensional electromagnetic element array of
claim 13, wherein the electromagnetic elements form part of a
pulsed source.
25. The integrated 3-dimensional electromagnetic element array of
claim 24, wherein the pulsed source is configured so that the
timing of switching between states is aligned with the delay in the
3-dimensional electromagnetic element array.
26. The integrated 3-dimensional electromagnetic element array of
claim 13, wherein the electromagnetic elements are configured as a
frequency selective filter.
27. The integrated 3-dimensional electromagnetic element array of
claim 13, wherein the electromagnetic elements are electronically
reconfigurable.
28. The integrated 3-dimensional electromagnetic element array of
claim 1, wherein the electromagnetic elements are electronically
reconfigurable.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority to U.S. Provisional
Application Ser. No. 61/349,148 entitled "Programmable
Electromagnetic Near- and Far-Field Manipulation" and filed May 27,
2010, the disclosure of which is incorporated by reference herein
in its entirety.
FIELD OF THE INVENTION
[0002] The present invention generally relates to integrated
antennas and more specifically to integrated 3-dimensional
electromagnetic element arrays.
BACKGROUND
[0003] The trend towards smaller available feature sizes in
integrated circuit processes enables systems and circuits operating
at ever higher frequencies. As a result, research and commercial
interests are moving towards circuits and systems operating in the
millimeter- and sub-millimeter wave regions using standard
integrated circuit technologies to provide less expensive and
mass-producible solutions compared to discrete designs.
[0004] Advances in packaging and thin film technologies allow the
integration of several integrated circuit dies or components,
possibly from different technologies or processes, into integrated
systems offering solutions in small form factors. Examples of such
systems include integration of processing units with cache memory
integrated circuit dies in a stacked configuration for thin form
factor packages, or integration of RF input or output amplification
stages with off-chip surface acoustic wave filters on a ceramic
substrate.
[0005] Among others, current areas of interest include radio
circuits and systems, sensors, continuous and pulsed power sources,
imaging systems and spectroscopic equipment operating at millimeter
and sub-millimeter wavelengths, sometimes also referred to as the
terahertz or far-infrared regime. In the millimeter-wave region,
applications for integrated receiver and transmitter systems
include car radar, communications systems and imaging systems for
personal and property security among others. In the sub-millimeter
wave region, so-called terahertz electronics is actively researched
with applications either envisioned or already marketed for
terahertz spectroscopy, short-distance communication, and medical
and process control imaging among others.
[0006] In all of the above cases, it is desirable to migrate,
whenever possible, towards commodity technologies (e.g. CMOS versus
hetero junction bipolar technologies) and higher levels of
integration to reduce costs, increase functionality and potentially
open new markets. As part of this drive, it is highly desirable for
millimeter- and sub-millimeter systems to integrate as much as
possible all components such as transmit and receive antennas and
electromagnetic sensors. One of the difficulties encountered is to
control the electromagnetic near- and far-fields as the wavelengths
become comparable to the physical dimensions of the circuit and
electromagnetic energy couples to the bulk and surrounding
dielectric (air) or has to be contained to the surface. This, in
turn, makes it difficult to implement truly versatile, broad-band
and efficient microelectronic circuits in these frequency
ranges.
[0007] Traditionally, integrated circuits are planar, that is they
are formed using process layers on the surface of a semiconductor
substrate. The substrate is then packaged using one of many
packaging options. In this context, the terms "antenna", "element"
or "electromagnetic element" are typically understood to mean any
circuit element electromagnetically interacting with the physical
environment. FIG. 1A illustrates a typical system package that
involves attaching an integrated electromagnetic element to a
ground plane. The package 10 includes an integrated electromagnetic
element 12 on a substrate 14 with a package ground-plane 16. The
substrate connects to external devices via wire bonds 18 and
package leads 20. A flip-chip packaging solution is illustrated in
FIG. 1B. The flip-chip package 30 also includes an integrated
electromagnetic element 32 on a substrate 34 that connects with
external devices via solder bumps 36 and ball pins 38. Other
packaging implementations are also possible, but all of these share
the planar nature of the electromagnetic elements due to the planar
nature of semiconductor processing.
[0008] In all of the implementations described above, trade-offs
can exist because electromagnetic boundary conditions are imposed
in a thin, effectively planar region (within the thickness
manipulated by the process). In particular, with the antennas and
electromagnetic elements constrained to a thin region in space,
trade-offs exist with respect to efficiency, versatility and usable
range of operation frequencies when attempting to manipulate the
electromagnetic environment. Versatility refers to the ability to
reconfigure the antenna. An example of a reconfigurable antenna
system is a phased array, where electronic reconfiguration achieves
directionality. Broad-band operation, meaning that the antenna can
operate over a wide range of frequencies is typically desirable,
because it allows greater freedom in system design and also lowers
the overall risk of malfunction as narrow-band antennas are
typically more susceptible to process and environmental
changes.
SUMMARY OF THE INVENTION
[0009] Three dimensional electromagnetic element arrays in
accordance with embodiments of the invention can be configured to
manipulate the electromagnetic near-field in a more efficient,
versatile and broadband fashion within integrated circuits and
systems than has been traditionally possible. Three dimensional
electromagnetic element arrays constructed in accordance with
embodiments of the invention can benefit any circuit or system that
changes electromagnetic near- and far-fields, such as integrated
receivers, transmitters, power sources, sensors, imaging or
spectroscopic systems, to name a few. In many instances, increasing
the efficiency of antennas and/or electromagnetic elements enables
the antenna(s) to radiate/receive at low passive loss. More broadly
speaking, the ability to control the impedance of an antenna can
facilitate interconnection with transmitter(s)/receiver(s).
[0010] One embodiment of the invention includes a first planar
integrated circuit, where the first planar integrated circuit
comprises at least a first integrated electromagnetic element, and
at least a second planar integrated circuit located on a different
plane to the first planar integrated circuit, where the second
planar integrated circuit comprises at least a second integrated
electromagnetic element. In addition, the first and second
integrated electromagnetic elements are configured to control the
near- and far-field pattern produced by the 3-dimensional
electromagnetic element array.
[0011] In a further embodiment, the first planar integrated circuit
is formed on the surface of a bulk resonator, and the second planar
integrated circuit is buried within the bulk resonator.
[0012] Another embodiment also includes a plurality of planar
integrated circuits buried at different depths within the bulk
resonator, where each integrated circuit includes at least one
integrated electromagnetic element. In addition, the
electromagnetic elements are configured to control the near- and
far-field pattern produced by the 3-dimensional electromagnetic
element array.
[0013] In a still further embodiment, electromagnetic elements are
configured to control the modes excited within the bulk
resonator.
[0014] In still another embodiment, the electromagnetic elements
are configured to control the directionality of energy radiated by
the bulk resonator.
[0015] In a yet further embodiment, the electromagnetic elements
are configured as an antenna.
[0016] In yet another embodiment, the antenna is a phased antenna
array.
[0017] In a further embodiment again, the electromagnetic elements
form part of an electromagnetic reflector.
[0018] In another embodiment again, the electromagnetic elements
form part of a shutter.
[0019] In a further additional embodiment, the electromagnetic
elements form part of a pulsed source.
[0020] In another additional embodiment, the pulsed source is
configured so that the timing of switching between states is
aligned with the delay in the 3-dimensional electromagnetic element
array.
[0021] In a still yet further embodiment, the electromagnetic
elements are configured as a frequency selective filter.
[0022] In still yet another embodiment, the bulk resonator
comprises a die stack, the first planar integrated circuit is
located on a first semiconductor substrate within the die stack,
and the second planar integrated circuit is located on a second
semiconductor substrate within the die stack.
[0023] In a still further embodiment again, the first planar
integrated circuit is located on the surface of the die stack, and
the second integrated circuit is buried within the die stack.
[0024] In still another embodiment again, the die stack further
comprises intermediate dielectric layers.
[0025] In a still further additional embodiment, at least the first
semiconductor region includes a region having different material
properties to the region on which the first planar integrated
circuit is formed.
[0026] Still another additional embodiment also includes
semiconductor optics formed on the die stack.
[0027] In a yet further embodiment again, the electromagnetic
elements are configured to control the modes excited within the die
stack.
[0028] In yet another embodiment again, the electromagnetic
elements are configured to control the directionality of the energy
radiated by the bulk resonator.
[0029] In a yet further additional embodiment, the 3-dimensional
electromagnetic element array is configured as an antenna.
[0030] In yet another additional embodiment, the antenna is a
phased antenna array.
[0031] In a further additional embodiment again, the
electromagnetic elements form part of an electromagnetic
reflector.
[0032] In another additional embodiment again, the electromagnetic
elements form part of a shutter.
[0033] In another further embodiment, the electromagnetic elements
form part of a pulsed source.
[0034] In still another further embodiment, the pulsed source is
configured so that the timing of switching between states is
aligned with the delay in the 3-dimensional electromagnetic element
array.
[0035] In yet another further embodiment, the electromagnetic
elements are configured as a frequency selective filter.
[0036] In another further embodiment again, the electromagnetic
elements are electronically reconfigurable.
[0037] In another further additional embodiment, the
electromagnetic elements are electronically reconfigurable.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1A is a conceptual illustration of a typical system
package containing an integrated electromagnetic element mounted on
a ground plane.
[0039] FIG. 1B is a conceptual illustration of a prior art
flip-chip package containing an integrated electromagnetic
element.
[0040] FIG. 2 is a conceptual illustration of a package containing
an integrated 3-dimensional electromagnetic element array formed
using a die stack in accordance with an embodiment of the
invention.
[0041] FIGS. 3A and 3B are three dimensional conceptual
illustrations of a bulk resonator formed from a die stack of four
doped semiconductor substrates on which dipole electromagnetic
elements are formed in accordance with embodiments of the
invention. Details such as bonding pads and integrated circuitry
are omitted for clarity.
[0042] FIG. 4 is a three dimensional conceptual illustrations of
packaging containing an integrated 3-dimensional electromagnetic
element array including spiral electromagnetic elements in
accordance with embodiments of the invention. Details such as
bonding pads and integrated circuitry are omitted for clarity.
[0043] FIG. 5 is a conceptual illustration of a package containing
an integrated 3-dimensional electromagnetic element array formed
using a die stack including intermediate dielectric layers in
accordance with an embodiment of the invention.
[0044] FIG. 6A is a chart showing simulated radiation efficiencies
for an electromagnetic element located at different depths within a
250 .mu.m bulk resonator.
[0045] FIG. 6B is a chart that compares the efficiency versus
frequency of a 2-dimensional electromagnetic element array and a
3-dimensional electromagnetic element array in which
electromagnetic elements are buried within the bulk resonator in
accordance with embodiments of the invention.
[0046] FIG. 7A is a chart that compares antenna gain versus
frequency for a 2-dimensional electromagnetic element array and a
3-dimensional electromagnetic element array in which
electromagnetic elements are buried within the bulk resonator in
accordance with embodiments of the invention.
[0047] FIG. 7B is a chart that compares antenna gain versus
frequency for different 3-dimensional electromagnetic element
arrays in which electromagnetic elements are buried within the bulk
resonator in accordance with embodiments of the invention.
[0048] FIG. 8 is chart that compares matched gain versus frequency
for a 2-dimensional electromagnetic element array and a
3-dimensional electromagnetic element array in which
electromagnetic elements are buried within the bulk resonator in
accordance with embodiments of the invention.
[0049] FIGS. 9A-9F are polar plots of simulated radiation patterns
for 2-dimensional planar electromagnetic element arrays at
different frequencies from 250, 300, 400, 450, 500, and 550 GHz
respectively.
[0050] FIGS. 10A-10F are polar plots of simulated radiation
patterns for 3-dimensional planar electromagnetic element arrays
including buried electromagnetic elements in accordance with
embodiments of the invention at different frequencies from 250,
300, 400, 450, 500, and 550 GHz respectively.
[0051] FIG. 11A is a power flow diagram corresponding to a bulk
resonator containing a 3-dimensional electromagnetic element array
including buried electromagnetic elements with electromagnetic
energy flow directed towards the air.
[0052] FIG. 11B is a power flow diagram corresponding to a bulk
resonator containing a 3-dimensional electromagnetic element array
including buried electromagnetic elements with electromagnetic
energy flow directed within the bulk resonator.
[0053] FIGS. 12A-12D are graphs illustrating simulated radiation
patterns for a pulsed source implemented using a 2-dimensional
planar array of electromagnetic elements and a pulsed source
implemented using a 3-dimensional array of electromagnetic elements
including electromagnetic elements buried within the bulk resonator
in accordance with an embodiment of the invention.
[0054] FIG. 13 is a chart illustrating the normalized antenna gain
for a variety of passive 2-dimensional planar electromagnetic
element arrays and 3-dimensional electromagnetic element arrays
that include buried electromagnetic elements, where the antenna
arrays are optimized for different frequencies.
[0055] FIG. 14 is a chart illustrating the antenna gain for a
variety of actively driven 2-dimensional planar electromagnetic
element arrays and 3-dimensional electromagnetic element arrays
that include buried electromagnetic elements, where the antenna
arrays are optimized for different frequencies.
[0056] FIG. 15 is a power flow diagram corresponding to a bulk
resonator containing a 3-dimensional electromagnetic element array
including electromagnetic elements buried within the bulk resonator
in accordance with embodiments of the invention, when
electromagnetic energy flow is directed upward.
DETAILED DESCRIPTION
[0057] Turning now to the drawings, systems and methods for
constructing integrated three dimensional (3-dimensional)
electromagnetic element arrays using a bulk resonator are
illustrated. In several embodiments, the integrated 3-dimensional
electromagnetic element arrays include electromagnetic elements
buried within the bulk resonator. In many embodiments, inclusion of
a third dimension in the electromagnetic element array can
alleviate or eliminate the trade-offs that are experienced in
conventional integrated antennas by using the third physical
dimension to provide an additional degree of freedom to manipulate
electromagnetic boundary conditions in the near-field of the
substrate, affecting both the resulting electromagnetic near- and
far-fields. In several embodiments, 3-dimensional electromagnetic
element arrays are formed by mechanically stacking substrates on
which integrated planar circuits are formed (i.e. chips) using
conventional die stacking techniques. In a number of embodiments,
the stack of substrates is integrated with optics by using
materials other than doped silicon as part of the stack. In
addition, since doped semiconductor materials typically have a loss
tangent, in a number of embodiments thinned semiconductor dies are
stacked on top of intermediate dielectric layers that can have
different properties to influence the properties of the bulk
resonator. In many embodiments, the intermediate dielectric layers
reduce losses without sacrificing the advantages gained by
utilizing an integrated 3-dimensional electromagnetic element
array. In a number of embodiments, the dielectric layers are
regions of different doping and/or permittivity in the
semiconductor substrates used to form the die stack.
[0058] In applications where a certain electromagnetic field
configuration in the near- and/or far-field of the integrated
circuit is desired, for example radiation emanating (or arriving)
from/to the integrated circuit, a traditional integrated circuit
typically can only influence the boundary conditions on the surface
of the circuit due to the planar nature of the processing.
Moreover, antennas at the surface of the semiconductor excite
substrate mode ratios determined by the substrate height, backplane
and physical properties of the substrate. As a result, similar
elements on the surface excite the same or similar ratios of
substrate modes irrespective of their location on the surface. This
severely limits the space of achievable electromagnetic field
configurations, and directly leads to the trade-offs mentioned
above. Where an electromagnetic field configuration is desired at
the surface as well as in the bulk of the substrate, employing
electromagnetic elements in the third dimension enables additional
degrees of freedom in influencing the near- and far-field. In
particular, structures buried in the substrate can excite different
ratios of substrate modes compared to surface-only structures,
effectively adding a dimension of control that is otherwise not
obtainable with planar only structures. The construction and
performance of integrated 3-dimensional electromagnetic element
arrays and their use in a variety of classes of device in
accordance with embodiments of the invention are discussed further
below.
Integrated 3-Dimensional Electromagnetic Element Arrays
[0059] Distributing electromagnetic elements in a three dimensional
manner throughout a bulk resonator can improve the efficiency,
directivity, and versatility of the antenna. In this way, three
dimensional arrays of electromagnetic elements can be utilized to
implement various devices including but not limited to transmit and
receive antennas, electronically controlled shutters, traps and
reflectors (mirrors) for electromagnetic energy, frequency
selective filters, and artificial anisotropic materials.
[0060] A bulk resonator in which a 3-dimensional array of
electromagnetic elements is formed can be constructed using
conventional semiconductor processing and die stacking
technologies. In addition, the types of electromagnetic elements
that can be utilized in these devices is typically not limited
other than by the requirements of a specific application.
Conceivably, processes can be developed to fabricate semiconductor
dies in which 3-dimensional arrays of electromagnetic elements are
formed, including 3-dimensional arrays of electromagnetic elements
in which electromagnetic elements are buried within the bulk
resonator. Utilizing such processes, a single layer bulk resonator
can be constructed that includes a 3-dimensional array of
electromagnetic elements in accordance with embodiments of the
invention. The construction of integrated 3-dimensional
electromagnetic element arrays using die stacking techniques in
accordance with embodiments of the invention is discussed further
below.
Integrated 3-Dimensional Electromagnetic Element Arrays Formed
Using Die Stacks
[0061] A package containing an integrated 3-dimensional
electromagnetic element array formed using a die stack in
accordance with an embodiment of the invention is conceptually
illustrated in FIG. 2. The package 100 includes a plurality of
doped semiconductor dies 102 on which electromagnetic elements 104
are integrated. The doped semiconductor dies are stacked so that
the entire stack acts as a single bulk resonator and so that some
of the electromagnetic elements are buried in the resulting bulk
resonator. The stacked dies are connected to package leads 106 by
wire bonds 108. In the illustrated embodiment, the electromagnetic
element array is formed by electromagnetic elements formed using
three layers of integrated circuits, two of which are buried within
the bulk resonator formed by the stacked substrates. The packaging
100 provides a ground plane layer 110. Although a three layer
electromagnetic element array is shown in FIG. 2, electromagnetic
elements can be located at any number of different depths within a
bulk resonator as appropriate to the requirements of a specific
application in accordance with embodiments of the invention.
[0062] A bulk resonator formed from a die stack including four
layers of electromagnetic elements in accordance with embodiments
of the invention is illustrated in FIGS. 3A and 3B. In the
illustrated embodiment, a bulk resonator 140 is formed from a stack
of four doped semiconductor dies 142. Integrated electromagnetic
elements are formed on the surface of each die within the die
stack. A plurality of dipole-shaped electromagnetic elements is
formed on the surface of each die within the die stack. Several of
the dipole-shaped electromagnetic elements 144 are on the surface
of the bulk resonator 140, and the dipole-shaped electromagnetic
elements formed on the surface of the other dies in the die stack
are buried within the bulk resonator 140. As is discussed further
below, inclusion of electromagnetic elements in a third dimension
can provide greater control over the electromagnetic far- and
near-field of the device improving its efficiency, directionality
and versatility. Although dipole-shaped electromagnetic elements
are shown in FIGS. 3A and 3B, any of a variety of electromagnetic
elements appropriate to a specific application can be utilized in
accordance with embodiments of the invention.
[0063] Packaging containing an integrated 3-dimensional antenna
formed using three semiconductor substrates on which spiral shaped
electromagnetic elements are formed in accordance with an
embodiment of the invention is illustrated in FIG. 4. The packaging
160 includes a bulk resonator formed from three semiconductor dies
162 on which spiral electromagnetic elements 164 are formed. As
with the integrated 3-dimensional antenna shown in FIGS. 3A and 3B
spiral electromagnetic elements 164 are located on the surface of
the bulk resonator and are buried (not shown) in the bulk
resonator.
[0064] The construction of integrated 3-dimensional antennas in
accordance with embodiments of the invention is not limited to
stacks of integrated silicon die alone. For example, processes can
be developed that can construct a single layer bulk resonator
containing a 3-dimensional electromagnetic element array. In
addition, electronics and electromagnetic elements can be
completely integrated with optics using materials other than doped
silicon as part of the die stack. Additional techniques for
constructing 3-dimensional electromagnetic element arrays in
accordance with embodiments of the invention are discussed further
below.
Integrated 3-Dimensional Antenna Arrays Incorporating Intermediate
Dielectric Layers
[0065] In many embodiments, since doped semiconductor materials
typically have a loss tangent, an integrated 3-dimensional
electromagnetic element array is constructed using a die stack of
thinned semiconductor dies separated by intermediate dielectric
layers. In a number of embodiments, the intermediate dielectric
layers are constructed from undoped semiconductor material or other
materials that reduce losses. In a number of embodiments, the
dielectric layers are regions of different doping and/or
permittivity in the semiconductor substrates used to form the die
stack and contribute to the material properties of the overall bulk
resonator.
[0066] A package including an integrated 3-dimensional
electromagnetic element array similar to the package shown in FIG.
2 with the exception that the die stack includes intermediate
dielectric layers in accordance with embodiments of the invention
is illustrated in FIG. 5. In the illustrated embodiment, the die
stack is formed from doped semiconductor dies 104 separated by
intermediate dielectric layers 180. In many embodiments the
intermediate dielectric layers are made from undoped semiconductor
material. In other embodiments, any of a variety of materials that
reduce losses within the bulk resonator formed by the die stack can
be utilized in the construction of the intermediate dielectric
layers.
Design of Integrated 3-Dimensional Electromagnetic Element
Arrays
[0067] When designing integrated circuit antennas, the immediate
electromagnetic surrounding is typically taken into account. This
includes the type of antenna used as well as packaging options.
Besides packaging options such as flip-chip or attaching the
integrated circuit to a ground plane, designers currently have a
choice over substrate thickness (typically with minimum and maximum
boundaries). The choice of substrate thickness affects traditional
integrated antennas whenever electromagnetic energy is coupled into
the substrate. Some antenna structures such as patch-antennas do
not couple into the bulk substrate, as they provide close-by return
current paths, but these antennas can have disadvantages in some
applications, most notably their narrow-band nature, as the
effective substrate is a thin film in the vicinity of the top of
the die. Substrate thickness plays a role because it affects the
available substrate modes, which are typically undesirable for
integrated antennas as they confine electromagnetic energy into the
substrate leading to energy losses.
[0068] In many conventional antennas, the strength of the induced
substrate modes and hence the incurred losses is a function of
frequency and substrate thickness, and since all electromagnetic
elements in a traditional integrated planar array have the same
spacing from the back-side, no additional degrees of freedom for
influencing the relative strengths of excited modes exists by
employing an array. By thinning the substrate, fewer substrate
modes exist and hence losses are generally lower and achievable
bandwidths are wider. However, with thinner substrates, controlling
the directionality of an antenna beam becomes very difficult as
electromagnetic energy easily leaks out in many directions. Thus,
using planar integrated circuit antennas typically limits
achievable performance because currents are limited to a surface
and will excite the same ratio of different substrate modes.
Improving Antenna Efficiency
[0069] Increasing the dimensionality of an antenna array to include
a third dimension and, in many embodiments, electromagnetic
elements buried within the bulk resonator allows an additional
degree of freedom in controlling the substrate modes that are
excited or absorbed. In the ideal case, the entire near-field in
the bulk resonator can be influenced and hence any interaction with
the outside world can be realized, whereas in the planar case not
enough boundary conditions exist leading to the trade-offs
mentioned above.
[0070] To illustrate this point, the radiation efficiency into free
space (air) of a single, optimally sized dipole on top of an
infinite (x,y-extent) silicon substrate on top of a ground plane at
different heights is shown in FIG. 6A. In the simulation
illustrated in FIG. 6A, silicon and metals are assumed lossless and
the antenna is positioned at various heights within the substrate.
Most notably, antennas buried in the substrate exhibit different
behavior over frequency compared to surface antennas because they
excite different bulk/substrate modes. Therefore, having control
over antennas in three dimensions compared to two provides
additional degrees of freedom and can therefore greatly alleviate
the trade-offs mentioned above.
[0071] The efficiency for upwards radiation for a 3-dimensional
antenna can be compared to the 2-dimensional case. FIG. 6B compares
radiation efficiencies for the case of an integrated 3-dimensional
antenna versus a planar 2-dimensional case. The quantity actually
maximized is directionality. As can be appreciated from FIG. 6B,
the integrated 3-dimensional antenna achieves higher efficiency
over a wider frequency range.
Improving Antenna Directionality
[0072] Directionality over a broad frequency range can be improved
by using 3-dimensional electromagnetic element arrays compared to
2-dimensional planar electromagnetic element arrays as is
illustrated in FIG. 7A. In the illustrated embodiment, the power
radiated upwards into free space is maximized for 2-dimensional and
3-dimensional electromagnetic element arrays on a 250 .mu.m thick
infinite silicon substrate. To determine the drive at each
electromagnetic element, an s-parameter solver minimizing input
power while keeping the detected power at a sense antenna in the
up-direction constant can be used that iteratively solves for the
optimum. Predicted and simulated results are shown in FIG. 7A.
Comparing the performance of the 3-dimensional electromagnetic
element array (200) and the 2-dimensional planar electromagnetic
element array (202) illustrates that the mere presence of
electromagnetic elements at depth improves performance. Remaining
discrepancies are due to the available simulation grid fineness in
the tool that was used for the simulation and its memory
requirements. FIG. 7B shows a graph comparing two different
3-dimensional electromagnetic element array configurations (one
sparse, and one dense) that differ in the positioning and number of
electromagnetic elements. Using a sparser set of electromagnetic
elements, simulation accuracy is improved.
[0073] Sideway radiation can also be significantly improved using
electromagnetic elements located within a bulk resonator. To
illustrate the performance improvement that can be achieved, a
simulation can be performed using an electromagnetic element array
that is symmetric in the E-plane. In the simulation, the 45.degree.
direction is optimized. The results of the simulation are shown in
FIG. 8. The chart shown in FIG. 8, illustrates that the matched
gain achieved in the desired direction is improved using a
3-dimensional array of electromagnetic elements (205) when compared
with a 2-dimensional planar array (206). FIGS. 9A-9F show polar
plots of radiation patterns simulated for the 2-dimensional array
of electromagnetic elements versus elevation for different azimuths
at 250, 300, 400, 450, 500, and 550 GHz respectively. FIGS. 10A-10F
show polar plots of radiation patterns simulated for the
3-dimensional arrays of electromagnetic elements versus elevation
for different azimuths at 250, 300, 400, 450, 500, and 550 GHz
respectively. Besides the improvement in directionality achieved
with the 3-dimensional array of electromagnetic elements, the
patterns for the 3-dimensional electromagnetic element array
exhibit lower side-lobe levels.
[0074] The 3-dimensional antenna arrays outlined above can be
utilized to implement a variety of different classes of device
having improved efficiency, directionality, and versatility
compared to that of a device constructed using a 2-dimensional
planar antenna array. Different types of integrated 3-dimensional
electromagnetic element array based devices in accordance with
embodiments of the invention are discussed below.
Integrated Transmit and Receive Antennas
[0075] In many embodiments, the techniques described above are
utilized to construct an integrated 3-dimensional transmit/or
receive antenna. The performance of antennas and antenna arrays for
both transmit and receive modes can be significantly improved using
3-dimensional arrays of electromagnetic elements compared to
2-dimensional planar arrays of electromagnetic elements. This has
been demonstrated in simulations using active amplitude- and
phased-arrays. The technique is not limited to such arrays, but
also applicable to reflect single antennas in reflect arrays (that
contain a single power source and integrated reflectors).
[0076] Integrated antennas and antenna arrays can benefit from the
use of 3-dimensional electromagnetic element arrays, because the
inclusion of a 3-dimensional array of electromagnetic elements
enables greater control over both the electromagnetic far- and
near-field in order to obtain a desirable electromagnetic far-field
pattern with minimal energy loss and optimal directionality.
Besides the far-field electromagnetic pattern that antennas
ultimately strive to achieve, it is important to emphasize that the
improvements described above are achieved by manipulating both
electromagnetic field domains.
Active, Electromagnetically Manipulated Shutters and Reflectors
[0077] Electromagnetic near-field manipulation using 3-dimensional
electromagnetic element arrays can be utilized to implement a
variety of different classes of device. Examples of such devices
are electronically manipulated shutters and reflectors (or
mirrors), in other words structures that are transparent or
reflective to incoming radiation. Those structures can be used to
guide radiation within the bulk resonator or through a substrate
interface. For example a shutter could be used to block or trap
energy inside a substrate (by reflecting energy back) until it is
"opened" (i.e. made transparent).
[0078] The ability of 3-dimensional electromagnetic element arrays
to guide radiation within a bulk resonator in accordance with
embodiments of the invention is illustrated in FIGS. 11A and 11B.
FIGS. 11A and 11B illustrate a slab 220 of lossless, silicon bulk
material of 250 .mu.m thickness placed on a conducting ground
plane, and including two dipole antennas 222, one on each end.
These dipoles, at a depth of 125 .mu.m, are test dipoles to excite
and sense electromagnetic energy flow inside the substrate
(approximately 65% of the energy excites substrate modes in this
setup). Between the two dipoles an array of electromagnetic
elements (224) is located, where the electromagnetic elements are
manipulated passively (i.e. they do not absorb or radiate energy)
and, in tandem, act as a reconfigurable reflector.
[0079] FIG. 11A illustrates a power flow diagram when the
electromagnetic element array (224) is reactively loaded to
maximize the radiated energy, while minimizing the energy to the
bulk sensing antenna 222. The values illustrated in FIG. 11A and
discussed below are obtained by optimizing the electromagnetic
element array for radiated power using a simulation involving a
specific configuration of sense antennas. In the illustrated
embodiment, submitted power is 3.21 mW, with 95.8 uW detected at
the sense antennas (2.98% of the submitted power sensed versus
1.44% sensed when an equivalent 2-dimensional antenna array is
used, corresponding to approximately 3 dB higher directivity). The
bulk sensor receives 131 nW, corresponding to 0.04% of the power
submitted (an equivalent 2-dimensional antenna array achieves
0.12%).
[0080] Using the 3-dimensional electromagnetic element array to
direct the energy towards the bulk sensing antenna 222 results in
the power flow shown in FIG. 11B. Of the 4.07 mW submitted, 1.59 mW
is absorbed in the bulk sense antenna 222, and 2.02 mW is radiated
into air. Because only 65% of the power is directed towards bulk
modes, 1.4 mW of the 2.02 mW would have been radiated in any case
(since the element array is several wavelengths away) and that the
additional "spill-over" radiation is as low as 600 .mu.W. This
demonstrates significant entrapment of power in the bulk resonator
can be achieved.
[0081] Using electromagnetic elements in a full 3-dimensional
arrangement; programmable reflectors can be implemented in
accordance with embodiments of the invention with significantly
improved directivity compared to an equivalent two-dimensional
planar array of electromagnetic elements. Because all manipulation
was accomplished using reactive tunings only, reprogrammable
structures that can selectively reflect, entrap and/or direct the
flow of energy can be implemented in accordance with embodiments of
the invention.
Using Electronically Manipulated Reflectors to Create Pulsed
Sources
[0082] Electronically manipulated reflectors that can direct flow
of electromagnetic energy can be utilized in a variety of other
applications including (but not limited to) pulsed sources. A
pulsed source that uses a bulk resonator to selective trap energy
or, alternatively, radiate it can be implemented using a
3-dimensional array of electromagnetic elements in accordance with
embodiments of the invention. To illustrate the benefits of
utilizing a 3-dimensional array of electromagnetic elements versus
a traditional, planar dipole array, a comparison can be performed
by simulating both configurations in a lossy (1 S/m), 250 .mu.m
thick piece of silicon on a ground plane. The top-center
electromagnetic element in both cases is driven to supply power (at
450 GHz), and the remaining elements are reactively tuned to
selectively entrap energy in the substrate ("storage mode") or
radiate energy upwards ("radiation mode").
[0083] In the traditional planar case, during storage-mode, the
input source provides 124.6 .mu.W, of which 60.6% is radiated into
air due to imperfect containment. The input impedance seen at the
source is 20.2.OMEGA.+111.5j .OMEGA., corresponding to a quality
factor of 5.5 (the ratio of energy stored versus energy
dissipated). The power detected at the air sensor is 88.4 nW.
Switching to radiation-mode, input power increases to 253.2 .mu.W,
the input impedance seen changes to 43 .OMEGA.+107.8j.OMEGA.
(quality factor of 2.5) and radiation efficiency changes to 88.9%
with 2.84 .mu.W sensed at the sensor, an increase of 15 dB. From
the radiation pattern, the gain in the upward direction changes
from -3.2 dB to 5.8 dB (the sense antenna aperture shields some of
the outgoing radiation).
[0084] For the case of a 3-dimensional electromagnetic element
array, in the storage mode, the input power is 63.3 uW and power
sensed is 17.7 nW. Input impedance is 8.5.OMEGA.+102.9j.OMEGA.,
corresponding to a quality factor of 12. The radiation efficiency
is 24.1%. Therefore, significantly more energy is stored in the
bulk and leakage radiation is reduced significantly compared to the
planar case. Switching to radiation mode, the sensor now registers
7.74 uW with 323.9.OMEGA. input power. The antenna gain increases
from -7.3 dB to 9.62 dB in the upward direction compared to the
storage-mode. The input impedance is 45.2.OMEGA.+95.2j .OMEGA.,
corresponding to a quality factor of 2.
[0085] FIGS. 12A and 12B compare the radiation pattern for both
cases in the storage phase. FIG. 12A illustrates the radiation
pattern of the 2-dimensional electromagnetic element array during
the storage phase (radiation efficiency 60.6%, i.e. only 39.4% of
the energy is stored) and FIG. 12B illustrates the radiation
pattern of the 3-dimensional electromagnetic element array during
the storage phase (radiation efficiency 24.1% meaning that 75.9% of
the energy is stored). As can be readily appreciated, a significant
amount of power leakage occurs in the 2-dimensional electromagnetic
element array compared with the 3-dimensional electromagnetic
element array.
[0086] FIGS. 12C and 12D compare the radiation pattern for both
cases in the radiation phase. FIG. 12C illustrates the radiation
pattern of the 2-dimensional electromagnetic element array during
the radiation phase (radiation efficiency 88.9%) and FIG. 12D
illustrates the radiation pattern of the 3-dimensional
electromagnetic element array during the radiation phase (radiation
efficiency 72.5%). The higher directional gain, the larger contrast
between storage- and radiation modes (compared to the planar case),
as well as the increase in energy that can be stored in the bulk
(as evidenced by the larger quality factor in storage mode)
illustrate the usefulness of including electromagnetic elements in
a 3-dimensional electromagnetic element array when implementing
actively manipulated reflectors in accordance with embodiments of
the invention.
[0087] Because electromagnetic simulation tools only provide
steady-state solutions, it is difficult to predict time-transient
behavior of the devices described above since that requires
knowledge of delay in the system. However, delay is typically
related to the physical size of the system. When the timing of
switching between states is aligned with the delay in the system, a
pulsed source can be implemented that can provide higher
instantaneous power by utilizing the stored energy. The specifics
depend on the horizontal and vertical dimensions of the bulk
resonator. Similar techniques to those discussed above can be
utilized to implement a number of other devices that employ
3-dimensional arrays of electromagnetic elements to influence the
electromagnetic near-field to reflect, trap or block the flow of
electromagnetic energy for the purpose of achieving desirable
electromagnetic near- and far-fields including but not limited to
shutters, reflectors, and flow-directors. Other devices that can be
implemented using 3-dimensional arrays of electromagnetic elements
to influence the electromagnetic near-field in accordance with
embodiments of the invention are discussed below.
Active, Electromagnetically Manipulated Frequency-Selective
Filters
[0088] An integrated 3-dimensional array of electromagnetic
elements in accordance with embodiments of the invention can be
used to control the electromagnetic near- and far-fields across
frequencies. In many embodiments, 3-dimensional electromagnetic
element arrays are used to implement frequency-selective filters
that accept or reject electromagnetic energy depending on the
frequency of the radiation. Because the elements are electronically
tunable, the wavelength of highest absorption and/or rejection can
be tuned.
[0089] A comparison of the frequency selective characteristics of
3-dimensional and 2-dimensional electromagnetic element arrays is
illustrated in FIG. 13. The graph 240 shows the normalized antenna
gain with the normalization done such that the maximum gain in the
upwards direction is 0 dB. All solid lines are results for the
3-dimensional electromagnetic element array structure in accordance
with embodiments of the invention and all broken lines are results
for the traditional planar antenna array structure. Different
tunings (i.e. changes in reactive loads on all but the top-center
element) are shown. The 3-dimensional electromagnetic element array
provides superior contrast and full usability over the frequency
range, whereas the traditional, planar structure has low contrast
due to multiple peaks and reduced range as it cannot effectively
distinguish signals from 250 GHz to 350 GHz. Accordingly, a
3-dimensional electromagnetic element array can be utilized to
provide an effective frequency-selective receiver, which can be
useful in applications including but not limited to spectroscopic
applications. In a number of embodiments, the top-center element of
the frequency-selective receiver can use a wide-band power detector
and the side- and bulk elements only need to implement reactively
tuned electromagnetic elements (for example using varactors, which
are available with reasonable quality factors even in current,
high-volume commercial semiconductor processes) to implement a
frequency-tunable power detector.
[0090] Because of reciprocity, the above array also can be operated
as a transmit antenna tunable to a desired frequency range. This is
useful as antennas are sized for operation in a particular center
frequency. Because of reciprocity, in the case discussed here, the
center antenna operated actively could also be tuned to
transmit-rather than receive-within the range of frequencies
discussed, thus making it possible to construct antennas operable
over a wider range of frequencies when a 3-dimensional
electromagnetic element array is used.
[0091] In many embodiments, the 3-dimensional electromagnetic
element array is actively driven in such a way that each element is
excited by an impulse of varying amplitude and phase (but such that
the amplitude of the excitation is the same at all frequencies and
that the phase lead/lag increases proportionally with frequency).
The antenna gain of arrays in which amplitudes and phases at each
element are optimized to maximize radiation straight up at 250 GHz,
350 GHz, and 450 GHz is illustrated in FIG. 14. The amplitudes
applied are rounded off to within +/-5% of the center antenna
amplitude. Very little contrast is achieved for the traditional
planar case, whereas using a 3-dimensional array of electromagnetic
elements again provides superior contrast.
Artificial Anisotropic Materials
[0092] Anisotropic materials are materials with material properties
(such as permeability and permittivity) that are directionally
dependent. Such directional dependency, among other things, can be
useful to direct or block the flow of electromagnetic energy
depending on the direction of the flow. Because materials used in
standard commercial semiconductor processes are homogeneous,
anisotropy in typical materials is achieved artificially, by
placing elements that electromagnetically interact with the
environment. Placing electromagnetic elements throughout the bulk
resonator (not just on the surface) in accordance with embodiments
of the invention can change the effective electric properties of a
bulk resonator. Using planar elements only, the interaction is
limited to two physical dimensions and it is hence very difficult
to achieve anisotropy.
[0093] The ability of a 3-dimensional array of electromagnetic
elements to modify the electric properties of a bulk resonator can
be illustrated through simulation. For example, a simulation can be
performed using a long slab of 250 .mu.m thick lossless silicon
placed on a ground-plane with dipole antennas at 125 .mu.m depth on
each end. In this configuration, the dipoles radiate both into the
substrate as well as into air. In an infinite lossless substrate in
this configuration, the radiation efficiency is 35%, i.e. 35% of
the energy is radiated into air and 65% of the energy goes into the
substrate. The two antennas are separated by 2 mm. In the center
between the pair of dipoles are electromagnetic elements that are
reactively loaded such that they act individually as (so-called)
reflectors. The center elements are tuned to maximize the energy
flow between the end dipoles in one direction and minimize it in
the other direction with one end used as a transmitter and the
other as a receiver interchangeably. The quantity maximized is the
ratio of forward flow to reverse flow. In this configuration, the
3-dimension electromagnetic element array results is a ratio of
13.1 dB illustrating that flow can be directed to a much greater
extent when a 3-dimensional array of electromagnetic elements is
utilized.
[0094] The ability to direct energy flows crossing a semiconductor
to air interface can also be illustrated via simulation. In one
example, a 250 .mu.m piece of lossy (10S/m) bulk semiconductor
suspended in air is simulated. FIG. 15 illustrates the case where a
3-dimensional electromagnetic element array is constructed in which
electromagnetic elements are buried within the bulk resonator. The
electromagnetic elements are configured to maximize radiation in
the top direction. In the illustrated example, radiation efficiency
is 49.6% with gains of 5.6 dBi and -9.2 dBi in the top- and bottom
direction respectively, demonstrating the directivity of the
configuration.
Other Applications
[0095] The examples described above serve as illustrations for
possible applications. The principle of using the third dimension
for integrated electromagnetic elements can be extended to other
applications. In particular, using analogues from traditional
optics, a construction similar to that shown in FIG. 15 could also
be used to form programmable quasi-optical elements such as but not
limited to lenses, polarizers, mirrors, couplers and
frequency-selective filters among others where there are both
incoming and outgoing electromagnetic waves into and from the
3-dimensional programmable structure. In these applications, the
3-dimensional nature of the electromagnetic element array is used
to manipulate an incoming wave to produce an outgoing wave (i.e.
such as in lenses, polarizers, mirrors etc).
[0096] While the above description contains many specific
embodiments of the invention, these should not be construed as
limitations on the scope of the invention, but rather as an example
of one embodiment thereof. Accordingly, the scope of the invention
should be determined not by the embodiments illustrated, but by the
appended claims and their equivalents.
* * * * *